Putrescine (or 1,4-butanediamine) is a type of polyamine, such as spermidine and spermine, and is found in gram-negative bacteria and fungi. Since putrescine is present in a wide range of concentrations in various species, it is expected to play an important role in the metabolism of microorganisms. Putrescine is commonly produced by chemical synthesis through acrylonitrile and succinonitrile from propylene. The chemical synthesis uses the substances derived from petrochemicals as starting materials and uses toxic chemicals, and thus it is not environment-friendly and has a problem of oil depletion.
In order to resolve these problems, there has been much research on developing a method for biosynthesis of putrescine by using microorganisms, that is more environment-friendly and reduces energy consumption. According to current knowledge, putrescine can be biosynthesized through two pathways. In one pathway, ornithine is produced from glutamate and the ornithine is decarboxylated to synthesize putrescine. In the other pathway, arginine is synthesized from the ornithine, agmatine is produced from the arginine, and then putrescine is synthesized from the agmatine. In addition, there are other methods for synthesizing putrescine by using a target microorganism which is transformed with the enzymes involved in the known synthetic pathways of putrescine. For example, WO09/125924 discloses a method for producing putrescine at high yield by inactivating the pathway involved in the decomposition and utilization of putrescine in E. coli, by inactivating the pathway in which ornithine, a precursor of putrescine, is converted to arginine, and by enhancing the biosynthetic pathway of ornithine. An article published in 2010 discloses a method for producing putrescine at high concentration by introducing and enhancing the protein that converts ornithine to putrescine into Corynebacterium strains which are not capable of producing putrescine. In addition it discloses a method for producing putrescine from arginine by introducing E. coli-derived arginine decarboxylase and agmatinase into the strains. In this regard, the ornithine pathway produced about 50 times higher amount of putrescine than the arginine pathway (Schneider et al., Appl. Microbiol. Biotechnol. 88:4, 859-868, 2010).